MRC1-dependent scaling of the budding yeast DNA replication timing program

We describe the DNA replication timing programs of 14 yeast mutants with an extended S phase identified by a novel genome-wide screen. These mutants are associated with the DNA replication machinery, cell-cycle control, and dNTP synthesis and affect different parts of S phase. In 13 of the mutants, origin activation time scales with the duration of S phase. A limited number of origins become inactive in these strains, with inactive origins characterized by small replicons and distributed throughout S phase. In sharp contrast, cells deleted of MRC1, a gene implicated in replication fork stabilization and in the replication checkpoint pathway, maintained wild-type firing times despite over twofold lengthening of S phase. Numerous dormant origins were activated in this mutant. Our data suggest that most perturbations that lengthen S phase affect the entire program of replication timing, rather than a specific subset of origins, maintaining the relative order of origin firing time and delaying firing with relative proportions. Mrc1 emerges as a regulator of this robustness of the replication program.Eukaryotic cells replicate their DNA in a highly orchestrated manner. DNA synthesis is initiated at specific chromosomal sites (replication origins) and proceeds in a bidirectional manner. Different loci are replicated at different times during S phase, depending on their distance from the nearest replication origin and on the time at which that origin initiates replication. This temporal order is highly reproducible between cells and can change concomitantly with cell differentiation (Hiratani et al. 2008; Schwaiger et al. 2009).The process of DNA replication has been studied extensively. Replication origins are licensed during mitosis and early G₁, with the binding of ORC (origin recognition complex) and the subsequent recruitment of the minichromosome maintenance (MCM) complex (part of the replicative DNA helicase) (for review, see Bell and Dutta 2002; Aladjem 2007; Sclafani and Holzen 2007). The onset of S phase is marked by the induction of the Clb5-6 cyclins (for review, see Murray 2004) and the associated degradation of the cyclin-dependent kinase (CDK) inhibitor Sic1 (Verma et al. 1997), leading to the phosphorylation of MCM subunits (via the cell cycle kinase Cdc7–Dbf4), and the recruitment of DNA polymerases α and ɛ to licensed origins (via phosphorylated Sld2/Sld3; Tanaka et al. 2007; Zegerman and Diffley 2007). Origins are then activated, with DNA polymerases catalyzing the addition of dNTPs to primer–template junctions.Only little is known about the mechanism that regulates the timing at which specific origins are activated. Saccharomyces cerevisiae sic1 mutants, which enter S phase prematurely, replicate DNA from a smaller number of origins, presumably because of a failure to license a subset of origins (Lengronne and Schwob 2002). Late replication origins are inactive when the S phase cyclin CLB5 is deleted (Donaldson et al. 1998) and when cells are subjected to DNA damage (by methyl methanesulfonate [MMS]) or treated with hydroxyurea (HU), a drug that reversibly inhibits ribonucleotide reductase (RNR) required for reduction of nucleoside triphosphates (NTPs) to dNTPs. Notably, the replication checkpoint kinases Mec1 and Rad53 are required for this suppression (Santocanale and Diffley 1998; Shirahige et al. 1998). Recent work, however, demonstrated that rather than suppressing late origins, HU confers an overall slowdown of the replication program (Alvino et al. 2007).To obtain further insight into the regulators of the replication program, we performed a genome-wide screen for mutants with an extended S phase. A total of 14 genes were identified, nine of which were not previously associated with S phase duration. In 13 of the mutants, origin firing time appeared to scale with the duration of S phase. Scaling was lost, and numerous dormant origins were activated, in cells deleted for MRC1, a gene required for normal fork progression (Szyjka et al. 2005; Tourriere et al. 2005) and for transducing the checkpoint signal from Mec1 to Rad53 upon replication stress (Osborn and Elledge 2003).     

CT features of intrapulmonary lymph nodes confirmed by cytology

We retrospectively assessed the computed tomography features of intrapulmonary lymph nodes confirmed by cytology in 18 patients. The median size of the lymph nodes was 5.8 mm (range=3.3–8.5 mm). All were below the carina, and only one nodule, which was associated with an interlobar fissure, was over 20 mm from the chest wall. The nodules were oval, round, triangular, or trapezoidal; had sharply defined borders; were solid and homogenous; and were without calcification. Six nodules (33.3%) had a discrete thin tag extending to the pleura. Intrapulmonary lymph nodes can reliably be confirmed by fine needle aspiration with cytological diagnosis.     

Ethnic Variation in the Association of Hypertension With Type 2 Diabetes

Lifestyle changes occurring with urbanization increase the prevalence of both type 2 diabetes mellitus (T2DM) and hypertension (HTN). Yemenites who have immigrated to Israel have demonstrated a dramatic increase in T2DM but the prevalence of HTN in diabetic Yemenites is unclear. In a cross‐sectional study, the authors evaluated the prevalence of HTN and lifestyle patterns in Israelis with T2DM of Yemenite (Y‐DM) and non‐Yemenite (NY‐DM) origin. Y‐DM (n=63) and NY‐DM (n=120) had similar age (63±7 vs 64±7 years, P=.5), diabetes duration, diet adherence, and exercise patterns. Y‐DM had a lower prevalence of HTN (63%) than NY‐DM (83%) (P<.01). Furthermore, Yemenite origin was independently associated with lower prevalence of HTN (odds ratio, 0.3; 95% confidence interval, 0.12–0.71). Blood pressure was well controlled with fewer antihypertensive medications in Y‐DM than NY‐DM (P<.01). Even though lifestyle patterns were similar in the two groups, Y‐DM had a lower prevalence of HTN compared with NY‐DM and required fewer antihypertensive medications.     

The use of sonographic cervical length assessment for the prediction of time from induction to delivery

Objective: The objective of this study is to investigate the role of trans-vaginal cervical length measurement in the prediction of the interval to successful vaginal delivery after induction of labor with balloon catheter.

Methods: In this prospective study of cervical length measurement before induction of labor, singleton pregnancies that underwent induction of labor between 37 and 42 weeks of gestation were included. The data collected included trans-vaginal sonographic cervical measurements followed by digital cervical assessment. Bishop score was used to quantify digital assessment (before induction of labor).

Results: During the study period, 71 patients were included in the study. A statistically significant linear correlation was found between sonographic cervical length prior to induction of labor and the time of delivery (Pearson correlation 0.335; p values 0.005). Of the 57 vaginal deliveries, 27 patients had a cervical length of less than 28?mm. Patients with a cervical length of less than 28?mm had a significantly shorter time to delivery compared to patients with more than 28?mm length (20.4 versus 28.7, respectively; p value?=?0.019). Cervical length of 28?mm remained significantly correlated even after performing several logistic regression models in order to control for confounders such as parity and age. In addition, a correlation was found between Bishop scores of above 7 to the time to delivery.

Conclusions: Cervical length is correlated linearly to the time interval between induction of labor and delivery. A cervical length of less than 28?mm was found to be statistically significant in predicting a shorter time to delivery.     

Smoking and complications of endosseous dental implants

BACKGROUND: The purpose of this study was to compare the incidence of the complications and survival rate related to dental implants among smokers and non-smokers, and to evaluate the influence of smoking by analyzing data of 959 implants placed in 261 patients during the years 1995 to 1998. METHODS: Patients were divided into 3 groups: non-smokers, mild smokers (up to 10 cigarettes per day) and heavy smokers (more than 10 cigarettes per day); smokers were divided into 2 subgroups according to duration of smoking (less or more than 10 years). Complications included minor (spontaneous implant exposure), major (spontaneous implant exposure requiring surgical intervention), and implant failure. The influence of smoking was analyzed for the type of implant cover screw and immediate versus late implantation. RESULTS: The overall failure rate was 2% for non-smokers and 4% for all smokers. Minor and major complications were found in higher percentages (46%) in the smoking groups than in the non-smoking group (31%). A significantly higher incidence of complications was found among smokers who received dental implants with high cover screws (63%) compared to those who received dental implants with flat cover screws (27%). CONCLUSIONS: This study establishes a relationship between implant complications and smoking, implant type (external or internal hex), and time of implantation as significant factors. A higher incidence of complications was found in the smoking group, especially in implants that had a high cover screw. Most complications will not lead to failures. Immediate implants failed less frequently than non-immediate implants. Limiting or reducing smoking habits will decrease complications of endosseous dental implants.